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Coupling elasto-plastic behaviour of unsaturated soils with piecewise linear large-strain consolidation
Géotechnique ( IF 5.8 ) Pub Date : 2020-05-18 , DOI: 10.1680/jgeot.18.p.261
Shunchao Qi 1 , Paul Simms 2 , Farzad Daliri 3 , Sai Vanapalli 4
Affiliation  

Slurried soils or tailings are often deposited in layers that undergo complex stress paths in terms of desiccation and loading, as a given layer may undergo variable degrees of desiccation before burial by subsequent layers, which has implications for geotechnical stability and geo-environmental performance. Proper analysis therefore requires not only an effective coupling of unsaturated flow with large-strain consolidation, but also inclusion of hysteresis effects. This paper presents the development and testing of a coupled unsaturated flow–large-strain consolidation model, UNSATCON, initially formulated for only monotonic dewatering, to include such effects. UNSATCON operates by a novel numerical algorithm that ensures mass conservation and handles the saturated/unsaturated transition smoothly. Differently from conventional integration schemes commonly embedded in finite-element formulations, this algorithm, tracking the void ratio change explicitly for large deformation, is shown to be applicable for most constitutive models of unsaturated soils under one-dimensional or isotropic stress conditions. Three constitutive models are implemented: a modified state surface model and the original and a minor variant of the Glasgow coupled model (GCM). The numerical model is evaluated using a recently published experimental study on multilayer deposition of thickened gold tailings. The model adequately reproduces the essential features of the dewatering processes, including the irrecoverable deformation induced by desiccation, the interlayer water exchange governed by deformation and deformation-dependent hysteretic retention behaviour. All three implemented constitutive models can reasonably simulate these experimental observations, despite some trivial discrepancies in magnitude. Point-level inspection, however, reveals some fundamental differences that may have important practical implications. For example, the additional plastic strain that occurs in GCM type models over multiple wetting–drying cycles may explain observed trends in increased strength in the simulated experiment.

中文翻译:

分段线性大应变固结耦合非饱和土的弹塑性行为

泥土或尾矿经常沉积在干燥和载荷方面经历复杂应力路径的层中,因为给定的层在被后续层埋葬之前可能经历不同程度的干燥,这对岩土工程稳定性和地球环境性能具有影响。因此,正确的分析不仅需要有效地耦合非饱和流与大应变固结,还需要包括磁滞效应。本文介绍了不饱和流-大应变固结耦合模型UNSATCON的开发和测试,该模型最初是为仅单调脱水而设计的,其中包括了这种影响。UNSATCON通过一种新颖的数值算法进行操作,该算法可确保质量守恒并顺利处理饱和/不饱和过渡。与通常嵌入有限元公式中的常规积分方案不同,该算法明确跟踪大变形的空隙率变化,适用于一维或各向同性应力条件下的大多数非饱和土本构模型。实现了三个本构模型:修改后的状态表面模型以及格拉斯哥耦合模型(GCM)的原始版本和较小版本。使用最近发表的关于增厚的金尾矿的多层沉积的实验研究对数值模型进行了评估。该模型充分再现了脱水过程的基本特征,包括由干燥引起的不可恢复的变形,由变形控制的层间水交换以及与变形有关的滞后滞留行为。尽管在数量上有一些细微的差异,但所有三个已实施的本构模型都可以合理地模拟这些实验观察结果。但是,点级检查揭示了一些基本差异,这些差异可能具有重要的实际意义。例如,在GCM类型的模型中,在多个润湿-干燥循环中发生的附加塑性应变可能解释了在模拟实验中观察到的强度增加的趋势。
更新日期:2020-05-18
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